Toy construction sets provide an enjoyable and stimulating play experience that can develop spatial skills and creativity in children. Traditional toy construction sets include base blocks of one or more types that can be assembled to create a variety of structures. The educational value of a toy construction set is enhanced if more complex components, in addition to base blocks, are included. For example, some toy construction sets include gears that can be coupled to base blocks or to other structural components. One such toy construction set is disclosed in U.S. Pat. No. 6,315,628, to Quercetti. Quercetti discloses a composable base plate having a matrix of coupling bores. Quercetti also describes a complex element that is configured for coupling to the base block via a special element and a series of tubular and flanged elements, referred to by Quercetti as elements of the first and second kinds, respectively. The special element is described as having four pins protruding from its bottom surface for engaging the coupling bores in the base plate. Each complex element has at least one axle that can be received into a connection bore formed in a toothed wheel. While the toy construction set disclosed by Quercetti provides for the construction of relatively complex structures compared to construction sets that include only base blocks, it suffers from several disadvantages. In particular, some of the elements disclosed by Quercetti are relatively small and may present a choking hazard to small children. Furthermore, the toothed wheels of Quercetti cannot be attached directly to a base block, and also cannot be coupled to other toothed wheels. Therefore, the variety of structures that can be built with the components disclosed by Quercetti is limited. Accordingly, an improved toy construction set is needed.